The objective of this proposal is to further investigate the physiology of the isolated medial basal hypothalamus (MBH)-pituitary complex as it relates to luteinizing hormone (LH) release. To this end experiments are designed to determine the ability of the isolated MBH-pituitary axis to support LH release following electrochemical stimulation (ECS) of the arcuate median eminence (ARC-ME) region in female and male rats as an index of luteinizing hormone-releasing hormone (LH-RH) activity in the MBH. Blood samples will be obtained before and after ECS and analyzed for LH as an index of LH-RH activity. Experiments are also proposed to directly determine the content of LH-RH in the MBH at several times after CHD and to examine whether estrogen priming will affect the LH-RH concentration. Another set of experiments are designed to determine if some of the LH-RH in the MBH originates in the preoptic-suprachiasmatic (POA-SCN) region. The last set of experiments are proposed to further investigate the effects of partial and complete hypothalamic deafferentation on the concentration of estrogen receptor complexes in th MBH using estrogen receptor assays and autoradiography.